1. Field of the Invention
This patent application relates to a compressed air/gas dryer system for generating clean, dry air for use in industrial processes. More specifically this patent application relates to a refrigerant compressed air/gas dryer system comprising a singular monolithic construction and a replaceable filter.
2. Background
Atmospheric air is contaminated with varying concentrations of hydrocarbons, solid particles and water vapor. When compressed to a working pressure of 100 pound-force per square inch gauge (PSIG), the concentration of these contaminants is increased by a factor of eight to one. If these contaminants are not removed prior to entering a process distribution system they will damage air operated equipment, slow down or stop production, corrode the inside of pipes, spoil product, ruin processes, and drive up energy costs.
Moisture is a serious problem in compressed air systems. Since atmospheric air always contains some amount of moisture, measured in terms of relative humidity. Relative humidity is the ratio of moisture in the air compared to the capacity of moisture that volume of air is capable of holding at a specified temperature. When air is compressed, friction causes the actual air temperature to rise, greatly increasing its ability to hold moisture. At 100 PSIG the quantity of moisture commonly held in eight cubic feet of air is reduced in an area ⅛ its original size. The result of compression is hot, wet, dirty air.
A good general rule is that for every twenty degrees Fahrenheit (20° F.) the temperature of air decreases, its ability to hold moisture is reduced by 50%. As air passes through a plant piping system, the ambient conditions cause the compressed air to cool, causing the formation of liquid water. This water, coupled with particulate matter and oil/lubricant carry-over will cause numerous problems. The water will wash away lubricants from tools and machinery, spoil paint applications, rust the general system, and, if exposed to unfavorable ambient temperatures, freeze.
Particulate matter consists of atmospheric particles that are drawn into a plant piping system through the air compressor intake. Some air system components, along with scale build-up in piping, may introduce additional particulate matter. Particulates traveling through the air system will cause pressure drop to increase, valves and orifices to clog, and product to be spoiled. Particulate matter will clog orifices and valves, damage gear driven equipment, increase system pressure drop and contaminate product.
Airborne hydrocarbons, compressor oils and lubricants are harmful to all downstream equipment and processes. Today's high performance compressor lubricants can cause additional problems, and need to be removed before they cause irreversible damage. They will cause valve and gasket materials to fail, and wreak havoc on processing equipment. Residual oils and lubricants will cause valve wear, spoiled product and system contamination.
Therefore, it is essential to treat process air before it can do any damage to a process system. By drying and filtering compressed air, operation efficiency can be maximized, and equipment productivity and longevity can be greatly increased.
Presently, refrigerated compressed air/gas dryer systems utilize some basic components. For example, there is usually a heat exchange unit used to pre-cool air entering the dryer system and to reheat dry air before the air leaves the dryer. Various systems also use an evaporator for circulating refrigerant to promote condensation of water vapor followed by a means to drain-off the resultant condensation. Systems are further equipped with a filter to clean the compressed air/gas before the air/gas enters the dryer system and/or as the air/gas leaves the dryer system. Additionally, some systems utilize a filter as an intermediate stage component; such as after the evaporator and before the reheater. To date, there are no dryer systems contained within a single housing that efficiently allows the passage of compressed air/gas to flow through the system and exit both dry and filtered.
U.S. Pat. No. 5,794,453 discloses an apparatus for removing condensate from a gas. The system has a chiller to cool the gas followed by a separator to remove the condensed liquid. The dried gas is then sent through a reheater before exiting the apparatus. While this apparatus dries and reheats the gas, there are significant drawbacks to this design. First, there is no filtration of the gas to remove particulates or to further condense any remaining water vapor in the gas following chilling. Secondly, the device is inefficient as the hot incoming air is cooled only through the chiller, thus requiring more energy to run and a greater amount of refrigerant to cool the gas.
U.S. Pat. No. 6,470,693 describes a gas compressor refrigeration system. The system has a chiller to cool the gas followed by a separator to remove the condensed liquid. The dried gas is then sent through a reheater before exiting the apparatus. A closed-loop refrigerant system which supplies heat to the reheater and is then recharged to cool the gas in the chiller. While this apparatus dries and reheats the gas, there are significant drawbacks to this design. First, there is no filtration of the gas to remove particulates or to further condense any remaining water vapor in the gas following chilling. Secondly, the device is inefficient as the hot incoming air is cooled only through the chiller, thus requiring more energy to run and a greater amount of refrigerant to cool the gas.
U.S. Pat. No. 7,343,755 presents a gas drying system having a recuperator, a moisture separator, and a refrigerated section housed in a single unit. The recuperator has a pair of fluid flow paths in thermal communication such that incoming hot air is cooled by, and in turn warms, cooled air exiting the system. The incoming air is further chilled in the refrigerated section to cause water in the air to condense into liquid water. The liquid water is then separated from the gas in the separator section. While this apparatus dries and reheats the gas, there is no filtration of the gas to remove particulates or to further condense any remaining water vapor in the gas following chilling.
Importantly none of the example provided above, even combined, construct in a single, compact housing, all the necessary elements to dry and clean compressed air/gas, namely to precool incoming gas, to chill the gas to 33° F., to drain off resulting condensation and to coalesce any remaining water molecules, to remove particulates in the gas, to sense the liquid level (of coalesced condensate) and drain off as necessary, and to reheat exiting gas. Further, none of the above examples employ filtration, and more specifically, filtration using a replaceable filter.
Thus, there is clearly a long-felt need for a free-standing, cost effective, refrigerated compressed air/gas dryer system that dries and filters compressed air/gas in a single pressurized housing where the housing further comprises a replaceable coalescing filter; eliminating the need for bulky interconnecting means between subcomponents. Ideally, a refrigerated compressed air/gas dryer system that dries and filters compressed air/gas in a single pressurized housing is compatible with a variety of existing dryer systems.
It should be understood that there are other conventional components that, when combined with the refrigerant compressed air/gas dryer system of the present disclosure, fully constitute a finished dryer which is ready for use. Such additional conventional components include a condensing unit (refrigerant compressor, condenser that is either air or water cooled, receiver, accumulator, pressure switches), drain solenoids and valves, cabinetry, controls and wiring, etc.